A bookstore rents books to students for $2 per book. The cost of running the bookstore is $300 per hour. The numbers of books and the probabilities that the bookstore would rent them in an hour mimics the distribution of the outcomes of flipping four coins. The probability of
renting a number of books was observed to be the same as the number of heads that appear in a four-coin flip. This distribution is
represented in the table.

If its only income came from book rentals, the bookstore would have to rent books to —-
students each hour, on average, to break even.